[Perf] Linux/x64: 1 Regression on 9/13/2026 3:54:51 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [b9678dcc0e7bac74a0d6b669b39d1007359b0016](https://github.com/dotnet/runtime/commit/b9678dcc0e7bac74a0d6b669b39d1007359b0016)
Compare | [3c4631e63b1de4308e2965b149992b992c9f5318](https://github.com/dotnet/runtime/commit/3c4631e63b1de4308e2965b149992b992c9f5318)
Diff | [Diff](https://github.com/dotnet/runtime/compare/b9678dcc0e7bac74a0d6b669b39d1007359b0016...3c4631e63b1de4308e2965b149992b992c9f5318)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile

Benchmark | Baseline | Test | Test/Base | Test Quality | Edge Detector | Baseline IR | Compare IR | IR Ratio
-- | -- | -- | -- | -- | -- | -- | -- | --
|

• [CreateNew - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

![graph]()
[Test Report]()

### Repro
General Docs link: https://github.com/dotnet/performance/blob/main/docs/benchmarking-workflow-dotnet-runtime.md

```cmd
git clone https://github.com/dotnet/performance.git
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile*'
```

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateNew(capacity: 10000000)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

[Profiling workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-dotnet-runtime.md)
[Benchmarking workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/benchmarking-workflow-dotnet-runtime.md)

Start with the benchmark source at src/benchmarks/micro/libraries/System.IO.MemoryMappedFiles/Perf.MemoryMappedFile.cs and the linked CreateNew report. Run the provided benchmarks_ci.py command, then compare the baseline and test commits and inspect the generated performance report. Done means the regression is explained and a verified fix or triage outcome is recorded.

Written by the indexing model from the issue text.